// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_
#define CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_

#include <memory>

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/threading/thread.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "content/public/renderer/media_stream_audio_sink.h"
#include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"

namespace media {
class AudioBus;
class AudioParameters;
} // namespace media

namespace content {

// AudioTrackRecorder is a MediaStreamAudioSink that encodes the audio buses
// received from a Stream Audio Track. The class is constructed on a
// single thread (the main Render thread) but can recieve MediaStreamAudioSink-
// related calls on a different "live audio" thread (referred to internally as
// the "capture thread"). It owns an internal thread to use for encoding, on
// which lives an AudioEncoder (a private nested class of ATR) with its own
// threading subtleties, see the implementation file.
class CONTENT_EXPORT AudioTrackRecorder
    : NON_EXPORTED_BASE(public MediaStreamAudioSink) {
public:
    using OnEncodedAudioCB = base::Callback<void(const media::AudioParameters& params,
        std::unique_ptr<std::string> encoded_data,
        base::TimeTicks capture_time)>;

    AudioTrackRecorder(const blink::WebMediaStreamTrack& track,
        const OnEncodedAudioCB& on_encoded_audio_cb,
        int32_t bits_per_second);
    ~AudioTrackRecorder() override;

    // Implement MediaStreamAudioSink.
    void OnSetFormat(const media::AudioParameters& params) override;
    void OnData(const media::AudioBus& audio_bus,
        base::TimeTicks capture_time) override;

    void Pause();
    void Resume();

private:
    // Forward declaration of nested class for handling encoding.
    // See the implementation file for details.
    class AudioEncoder;

    // Used to check that we are destroyed on the same thread we were created on.
    base::ThreadChecker main_render_thread_checker_;

    // Used to check that MediaStreamAudioSink's methods are called on the
    // capture audio thread.
    base::ThreadChecker capture_thread_checker_;

    // We need to hold on to the Blink track to remove ourselves on destruction.
    const blink::WebMediaStreamTrack track_;

    // Thin wrapper around OpusEncoder.
    // |encoder_| should be initialized before |encoder_thread_| such that
    // |encoder_thread_| is destructed first. This, combined with all
    // AudioEncoder work (aside from construction and destruction) happening on
    // |encoder_thread_|, should allow us to be sure that all AudioEncoder work is
    // done by the time we destroy it on ATR's thread.
    const scoped_refptr<AudioEncoder> encoder_;
    // The thread on which |encoder_| works.
    base::Thread encoder_thread_;

    DISALLOW_COPY_AND_ASSIGN(AudioTrackRecorder);
};

} // namespace content

#endif // CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_
